I had the same squeek, it was driving me crazy. I tried the felt under the plastic bracket, but that didn't stop it. I finally narrowed it down to the seatbelt rubbing on the seat. So, I applied a small strip of Velcro (furry side) to the seat, right where the belt was touching. It eliminated the squeek completely.

 

I removed these hooks from mine. It is only a screw holding them on.

 

I removed my hooks years ago and my seats still do it. It's because I have the seats one notch from all the way back and one notch reclined causing the seat to rub slightly on the bulkhead near the top of the seat. I'm going to try a piece of felt velcroed onto the bulkhead in the appropriate position.

 

on the seat belt rubbing/creaking - the fuzzy side of a velcro strip is an excellent quick fix.

thanks for posting. my pics = your pics no need to use the additional bandwidth.